Revise: Pressure
Atmospheric pressure and the barometer, pressure in a liquid, the manometer, and the principles of Archimedes and Pascal.
P = F/A; atmospheric pressure ≈ 100,000 Pa at sea level, acting equally in all directions.
100,000 Pa over a 1.5 m² table exerts 150,000 N.
P = hρg; a barometer measures atmospheric pressure from a supported mercury column (~760 mm).
0.76 m of mercury gives P ≈ 101,293 Pa.
P = P₀ + hρg; pressure increases linearly with depth.
At 10 m depth in water, total pressure ≈ 198,000 Pa.
Buoyant force Fᵦ = ρVg equals the weight of fluid displaced.
Displacing 0.02 m³ of water gives 196 N of buoyant force.
F₁/A₁ = F₂/A₂; pressure in an enclosed fluid transmits equally, multiplying force.
A 0.02→0.5 m² piston ratio turns 100 N into 2500 N.
ΔP = hρg; a manometer compares gas pressure to atmospheric via liquid column height difference.
A 0.15 m mercury difference indicates a gas pressure roughly 20,000 Pa above atmospheric.